X-pipe & H-pipe really change the ........tone of the engine. 
To me...the X-pipe makes my 5.0 sound sorta like the new Mustangs when it revs-up. It has sortuva "tinny" sound.

A lot of the "publicity" about power increases with both pipes have kinda been debunked on street engines.
They DO help stabilize the exhaust system from vibration.
IF you have good money poured into your engine with big cam and heads it WILL quieten it way down.
(IF that's what you want)

I spent a lotta $$ to build this hot rod sooooo...I want it to sound like a hot rod!

I welded in cut-outs/dumps on my system just after the headers and before the exhaust pipes (2.5")
Great if you plan to maybe race it or (like me) jus-wanna-live-the-dream occasionally.
IF not...weld the joints.
(I did NOT weld the joints solid because in the future its wayyy EZ'er to cut the tacks than grind out the complete weld.)
Tailpipes to the rear valance make the  sound wayyy less.......uhhhhh....... tiring on a long road trip (like an MS Bash trip)
Muffler choices run the range in our group.
From "Old-man-quiet" like Mustangsteve to..... NO MUFFS-let'r-rip-tater-chip like DC! (and me) and everything in between.
6sally6

Nos681 wrote:

Flowmasters dumped in front of axle…it was loud outside and even louder at certain rpm’s inside.

 
^^^^^^ Here(Hear) was the noise issue!
The sound reflects up from the road and makes the car sound  'super-healthy'/ deafening  inside & out.
6sal6